当不存在后退按钮时，将左栏按钮项添加到 UINavigation控制器

Question

我想在我的导航栏中添加一个默认的左栏按钮项。仅当 UINavigationController 没有提供后退按钮时，它才应显示。

最好的方法是什么？

Answer 1

- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated {
    if(navigationController.viewControllers.count != 1) { // not the root controller - show back button instead
        return;
    }
    UIBarButtonItem *menuItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemOrganize
                                                                              target:self
                                                                              action:@selector(menuItemSelected:)];   
    [viewController.navigationItem setLeftBarButtonItem:menuItem]; 
}

Answer 2

Swift 代码添加leftBarButtonItem...

    let leftMenuItem = UIBarButtonItem(barButtonSystemItem: UIBarButtonSystemItem.Done, target: self, action: "leftMenuItemSelected:");
    self.navigationItem.setLeftBarButtonItem(leftMenuItem, animated: false);

更新

适用于 Swift 4 及以上

版本

    let leftMenuItem = UIBarButtonItem(barButtonSystemItem: .done, target: self, action: #selector(leftMenuItemSelected(_:)))
    self.navigationItem.setLeftBarButton(leftMenuItem, animated: false);

Answer 3

Swift 3 版本：

let done = UIBarButtonItem(barButtonSystemItem: .done, target: self, action: #selector(YourController.done))
navigationItem.setLeftBarButtonItem(done, animated: false)

Answer 4

适用于 Swift 4.x 及更高版本（5.x）

func addNavigationItemBtn(){
    let backBtn = UIBarButtonItem.init(title: "Menu", style: .plain, target: self, action: #selector(menuAction))
    self.navigationItem.leftBarButtonItem = backBtn
}
@objc func menuAction(){
    print("menu button pressed")  //Do your action here
}

Answer 5

Swift 4

let item = UIBarButtonItem(title: "Setting", style: .done, target: self, action: #selector(setting))
 navigationItem.rightBarButtonItem = item
// then do your action in function setting 
@objc
  final func setting() {
    print("Your work here.")
  }